Agelasidae Verrill, 1907

Łukowiak, Magdalena, 2015, Late Eocene siliceous sponge fauna of southern Australia: reconstruction based on loose spicules record, Zootaxa 3917 (1), pp. 1-65 : 13-15

Family Agelasidae Verrill, 1907

Verticillate styles and oxeas with whorls of tubercles regularly arranged along the spicule occur in the studied samples. These oxeas with whorls of short tubercles ( Fig. 2 B–D) are similar to these of Recent species Agelas axifera Hentschel, 1911 (compare with Fig. 3 ). Hentschel describes verticillate oxeas with 5–6 tubercles in each of 7–15 whorls arranged along the spicule, while the ones described here have 18–22 whorls that are more densely packed and consist of about 6–8 tubercles in each whorl. Also the size of the spicules is bigger—the spicules described by Hentschel are 112–152 µm long and the ones described here are approximately 250–300 µm long. Despite these differences, the assignment of these spicules to Agelas cf. axifera seems justified because today this species occurs along the western and eastern coasts of Australia (e.g., Champion Bay; Hooper & Wiedenmayer 1994, van Soest et al. 2013).

Also the small verticillate style ( Fig. 2 A) seems to have a recent equivalent among agelasid spicules. A spicule described here is similar to the spicules in the Recent Agelas wiedenmayeri Alcolado, 1984 and Agelas conifera ( Schmidt, 1870) . Both these species are noted today only from the Caribbean— A. wiedenmayeri is described from Cuba ( Alcolado 1984, fig. 8b) and A. conifera ( Schmidt, 1870) is reported from all around the Caribbean (compare with Zea & van Soest 1986, fig. 4A). The spicules also show a morphological similarity to other Caribbean species Agelas citrina Gotera & Alcolado, 1987 and A. clathrodes ( Schmidt, 1870) (compare with Parra-Velandia 2011, Ph.D. thesis, figs. 4B, F). This suggests that the discussed Eocene spicule may belong to different species of Agelas than those mentioned above.

Additionally, some other spicules ( Figs. 2 E–G) possessing whorls consisting of long spines of equal length that are similar to A. wiedenmayeri spicules (compare with Mothes 2007, fig. 13) have been here recorded. But similar spicules occur also in “sclerosponge” species Goreauiella auriculata Hartman, 1969 (order Agelasida , family Astroscleridae ). In both cases however, the spicules are much smaller than the ones described here and both, A. wiedenmayeri and G. auriculata were described only from the Caribbean Sea. The presence of two spicule morphotypes independently assigned to A. cf. wiedenmayeri (see discussion above) confirms such assignment.

In the rest of the cases ( Figs. 2 H–I), spicules are not characteristic enough to assign them to the lower taxonomic level than the family Agelasidae . These spicules may belong to the Recent species known from southern Australia, e.g., to A. cavernosa Thiele, 1903 , A. dendromorpha Lévi, 1993 , or A. semiglaber Pulitzer-Finali, 1996 . Especially the spicules of Agelas dendromorpha Lévi, 1993 resemble those described here, both, in morphology (e.g., the number of the whorls) and the size (compare with Lévi 1993, fig. 11A), but the studied spicules may also represent an extinct species.

It is worth mentioning that verticillate monaxial spicules occur also in other demosponge groups (e.g., the order Poecilosclerida ), but those assigned here to the family Agelasidae are characterized by regularly arranged whorls of tubercles, whereas monaxons of poecilosclerids usually have (with some exceptions, e.g., genus Sceptrintus Topsent, 1898 , family Podospongiidae ) an irregularly sculptured surface. Also one of the spicules described ( Fig. 2 G) is similar to the spicules of Alectona primitiva (family Thoosidae ) described by Vacelet & Vasseur (1971, fig. 22A) but the presence of other agelasid spicules and the lack of microscleres of this thoosid makes the agelasid assignment more probable.

The spicules similar to those assigned here as agelasids were also described by Schrammen (1924, pl. 4, figs. 29, 32) from the Cretaceous of NW Germany but without a precise assignment. On the other hand, sponges belonging to the family Agelasidae and the genus Agelas have already been described in the fossil record, e.g., by Mostler (1994, pl. 1) from the Permian of Texas. From Miocene of Central Atlantic this type of spicules was described by Burky (1978, pl. 10, fig. 1) and from rocks of the same age from the central Paratethys by Łukowiak et al. (2014, fig. 5H). However, it is the first fossil record of Agelas cf. axifera and A. cf. wiedenmayeri .

Figures

FIGURE 2. Spicules of sponges of the order Agelasida; A—Verticillate style of the family Agelasidae; B – D—Verticillate oxeas of Agelas cf. axifera, family Agelasidae; E – G—Verticillate oxeas of Agelas cf. wiedemayeri, family Agelasidae; H, I—Oxea and style of Agelas sp., family Agelasidae.

FIGURE 3. Acanthoxea of recent Agelas axifera (redrawn from Hentschel 1911).